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Posts tagged Evidence based medicine.

The 2nd Horseman: Quality Evidence

Our understanding of what makes for quality medical research has improved dramatically over the past three decades. We understand that research must be ethical; should be reproducible; free of bias, so that we may make accurate conclusions; and that confounders be minimised and controlled for. We understand that prospective is best, and large blinded randomized trials are king.

We can articulate that a study must be appropriately powered to answer the question we are asking – but also not over-powered so that we waste resources and goodwill, or continue a study after an answer is known.

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The 1st Horseman: Publication Overload

The number of new medical articles published each month is accelerating. PubMed has over 23 million indexed going back to 19661, adding around 500,000 every year – but that's just the articles they index. There are an estimated 50 million scholary articles in total ever written 2, and currently over 28,000 peer-reviewed journals in print, publishing almost 2 million new articles in 2012 – and that's growing by 3% every year.3

If we focus only on MEDLINE® citations (publications indexed with MeSH, Medical Subject Headings) the number of publications each year is increasing exponentially. The graph below shows annual (not cumulative) MEDLINE® citations. The trendline in orange highlights the challenge of staying-up-to-date: annual medical publications is not just increasing, its accelerating.

Publication Overload

source: http://www.nlm.nih.gov/bsd/medline_cit_counts_yr_pub.html

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  1. Wikipedia: PubMed. 

  2. Jinha, Arif E. Article 50 million: an estimate of the number of scholarly articles in existence. Learned Publishing, Volume 23, Number 3, July 2010, pp. 258-263(6). 

  3. The STM report 2012 - An overview of scientific and scholarly journal publishing

The Four Horsemen of the Medical Research Apocalypse

The evidence-based medicine movement started excitedly in the 1990s, filled with much promise and hope. The way we practice medicine has been improved by EBM, along with the health of our patients. However it has not been all smooth sailing, and the challenges to evidence-based medicine are growing not lessening.

While we know more about the human body, critical care, anesthesia, and resuscitation than ever before, it is conversely more difficult to integrate evidence and guide decisions where they matter: for an individual patient.

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Metoclopramide: it actually works!?

Metoclopramide had long been written off by many anesthetists and anesthesiologists, aware of trials and meta-analyses that show no or limited effect in treating or preventing nausea and vomiting – in particular limited ability to prevent post-operative nausea and vomiting (PONV). Most recently Henzi, Walder and Tramèr (1999) were able to show only very limited benefit for metoclopramide 10 mg in preventing vomiting and no significant effect in preventing nausea in adults.1,2,3

What is metoclopramide?

Metoclopromaide is a benzamide, predominately used for antiemesis and its gastric prokinetic effect. It is marketed under the names Maxalon®, Pramin® and Reglan® in various countries. Although considered an old drug its antiemetic action was first identified in 1964 by French doctors Justin-Besançon and Laville.3 (In contrast the analgesic tramadol is often considered a "modern" drug outside of Europe, but was launched by Grünenthal GmbH in 1977.)

Metoclopramide readily crosses the blood-brain barrier where it mediates anti-emetic effects primarily as a dopamine D2 antagonist in the chemoreceptor trigger zone (CTZ – located in the area postrema of the 4th ventricle). Metoclopramide also has mixed 5-HT3 receptor antagonist and 5-HT4 receptor agonist actions. The former may contribute to anti-emesis at higher doses and the later to its pro-kinetic effects. Muscarinic cholinergic actions have also been identified, both through increasing acetylcholine release and by increasing receptor sensitivity to acetylcholine in the upper GI tract – further contributing to the pro-kinetic effect.

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  1. Henzi I, Walder B, Tramèr MR. Metoclopramide in the prevention of postoperative nausea and vomiting: a quantitative systematic review of randomized, placebo-controlled studies. Br J Anaesth. 1999 Nov;83(5):761-71. 

  2. It's also interesting to note that there was no dose responsive effect regardless of route. NNT to prevent early (<6h) and late (<48h) vomiting were 9.1 (95% CI 5.5-27) and 10 (6-41) respectively. In children the best documented regimen was 0.25 mg/kg. NNT to prevent early vomiting was 5.8 (3.9-11); there was no effect on late vomiting. There was only a single documented case of extrapyramidal side effects out of 3260 patients, giving an incidence of 0.03%. 

  3. Justin-Besançon L, Laville C.C R Seances Soc Biol Fil. 1964;158:723-7. 

Critically appraising the evidence

It’s hard to keep up with the latest evidence. Not only is the sheer volume of newly published papers overwhelming and the variety of topics broad and wide, but then after finding a paper that piques your interest you are still faced with the tricky task of critically assessing the paper's quality and relevance. Metajournal aims to solve many of these problems, but sometimes you need to just sit down and drag that paper over the keel yourself.

One of the most useful tools I have found are checklists provided by the Critical Appraisal Skills Programme, a UK non-profit based in Oxford. CASP runs workshops that educate healthcare workers and others on how to appraised medical evidence — and they share online the great checklists they use during the workshop under a Creative Commons license.

Find → Appraise → Act

They provide a set of eight critical appraisal tools designed to be used when reading research, covering:

  1. Systematic Reviews
  2. Randomised Controlled Trials
  3. Cohort Studies
  4. Case Control Studies
  5. Economic Evaluations
  6. Diagnostic Studies
  7. Qualitative studies
  8. Clinical Prediction Rule

What will the 'Medical Journal of You' look like?

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